1. Field of the Invention
The present invention relates to a rotating electric machine stator, and more particularly, to a rotating electric machine stator in which coils are wound via insulators.
2. Description of Related Art
When coils of a rectangular wire are wound via insulators, the insulators are preferably as thin as possible in order to improve the space factor of the windings as long as the insulating performance of the insulators is ensured.
Japanese Patent Application Publication No. 2012-222944 (JP 2012-222944 A) discloses a stator in which rectangular wires are wound around teeth that protrude inward from a yoke portion of a stator core via insulators. In the stator, the thickness of the insulators is varied depending on the relative positional relationship between the rectangular wires and the teeth.
It is stated in Japanese Patent Application Publication No. 2013-162565 (JP 2013-162565 A) that concentrated winding coils that have been preliminarily formed by winding coil windings with a rectangular cross-section using a winding mold are fitted around teeth of a stator core from the radially inner side thereof.
It is stated in Japanese Patent Application Publication No. 2008-220093 (JP 2008-220093 A) that, when concentrated winding coils are sequentially fitted on teeth that protrude radially inward from a yoke portion of an integrated stator core, a coil cannot be fitted onto the last tooth unless a special measure is taken because coils have been already placed in the slots on both sides of the tooth. It is, therefore, disclosed that the coil is deformed in a hollow state before it is installed in order to improve the space factor without using a dividable core.
In connection with JP 2008-220093 A, it is pointed out in Japanese Patent Application Publication No. 2013-223288 (JP 2013-223288 A) that, when multilayer multistage concentrated winding coils are used and the coil to be fitted on the last tooth is deformed, the deformation causes gaps or interference between the multilayered windings. It is stated in the document that predetermined gaps are preliminarily provided between the windings of the multilayer coils in order to prevent interference therebetween.
In order to improve the space factor of coils while ensuring the insulating performance of insulators, the use of stepped insulators as described in JP 2012-222944 A is preferred. In this case, when concentrated winding coils are used in an integrated stator, the coil that is to be installed last must be deformed before it is installed as described in JP 2008-220093 A. At this time, when stepped insulators are used, the corner portions of the deformed coil may interfere with the steps of the insulator. Thus, because the coil must be installed carefully in order to avoid the interference, the coil insertability is poor. When the width of the teeth is reduced in order to improve the coil insertability, the space factor of the coils decreases, which can cause a decrease in performance of the rotating electric machine or other problems.